The present applicant has previously proposed various ways to focus solar rays or artificial light rays by the use of lenses or the like and to guide the same into an optical conductor cable, and thereby to transmit them onto an optional desired place. The solar rays or the artificial light rays transmitted and emitted in such a way are employed for photo-synthesis and for use in illumination or for other like purposes, as for example, to promote the cultivation of plants.
However, in the case of utilizng the light energy for cultivating plants as mentioned above, the light rays transmitted through the optical conductor cable have directional characteristics. Supposing that the end portion of the optical conductor cable is cut off and the light rays are emitted therefrom, the radiation angle for the focused light rays is, in general, equal to approximately 46.degree.. That is quite a narrow field. In the case of utilizing the light energy as described above, it is impossible to perform a desirable amount of illumination by simply cutting off the end portion of the optical conductor cable and by letting the light rays emit therefrom.
Therefore, the present applicant has already proposed various kinds of radiators capable of effectively diffusing the light rays which have been transmitted through an optical conductor cable and for radiating the same for the purpose of illuminating a desired area. The present invention extends the idea and, in particular aims at applying intensified light rays to a desired place and to keep the light source at a distance to plants and to move the light source back and forth in order to supply light rays over a wider area.